1. Field of the Invention
The present invention relates to a method and apparatus of stacking cards, printed sheets or similar products. More specifically, this invention is directed to apparatus having a plurality of product feeder stations situated in a row, a conveyor defining a channel and having pushers that propell the products along the channel as stacks are formed and receiver means located between the feeder stations and the channel for controlling the delivery of the products to the channel under the influence of the pushers.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in the stacking of landscape-formal cards or printed sheets. It is common practice in the art to form such printing work products into stacks for temporary storage or transportation. The previously available stacking apparatus, as exemplified by the disclosure of published German patent application 39 35 372, have had a number of inherent deficiencies.
Previous apparatus were designed for stacking small-format cards or printed sheets. The pushers associated with the conveying chain are positioned close to a lateral stop. When broadside or landscape-format cards or printed sheets are pushed from the receiving table of such apparatus the products have a tendency to twist. This twisting can be counteracted by the use of guide rails. However, the product may become skewed on the guide rail.
Furthermore, the product may lift upwardly during transport as a result of air flowing under the leading edge. This action is especially prevalent when the product is bowed to a convex shape. Current apparatus utilize drag springs to correct this problem. However, these springs are only effective if the product is composed of stiff material.